Earthquake that shook southwest Illinois Thursday was second this month
The U.S. Geological Survey reported an earthquake in southwest Illinois Thursday evening.
The earthquake was recorded in Clinton County, about a mile from Germantown, at about 6:55 p.m. It registered a 2.8 on the Richter Scale, according to the USGS.
It’s the second such tremor reported in southern Illinois in the last month. A 2.5-scale earthquake shook parts of Perry County near Pinckneyville on March 5. An earthquake also was recorded in the region on December 16, when a 3.1-magnitude event shook Washington County, about 12 miles southwest of Mount Vernon.
About 1 million earthquakes of similar magnitude occur globally each year and are usually felt by people close the epicenter, but cause no damage. According to the USGS, the territory of the quake is part of the Illinois Basin-Ozark dome region, which borders the New Madrid seismic zone.
The Illinois Basin-Ozark dome region covers parts of Indiana, Kentucky, Illinois, Missouri and Arkansas and stretches from Indianapolis and St. Louis to Memphis.
According to the Illinois Emergency Management Agency, the New Madrid Seismic Zone averages about 200 measurable “events” per year, most of which are not felt. Tremors between magnitude 2.5 and 3.0 occur annually with a 4.0 or greater about once every 18 months and 5.0 or above every 10 years.
The New Madrid Fault caused some of the largest earthquakes in U.S. history including 8.2- and 7.4- magnitude earthquakes on consecutive February days in 1811 and a series of quakes ranging from 7.0 to 8.6 in the winter of 1812.
The U.S. Geological Survey rates earthquakes on a scale relative to the amount of damage they can cause:
2.5 or less: Usually cannot be felt.
2.5-5.4: Often felt, but causes only minor damage. There are an estimated half-million worldwide each year.
5.5 to 6.0: There may be slight damage to buildings and other structures. They are more rare, though, with 350 or so annually.
6.1-6.9: The 100 that occur annually may cause significant damage in areas that are highly populated with a density of buildings.
